1. Field of the Invention
This invention relates to the field of catheters and, more particularly, relates to a method and to a system for inserting catheters for administering spinal anaesthesia.
2. Description of the Prior Art
Catheter placement devices and related methods involve puncturing of a membrane or like tissue by means of a hollow needle within which a catheter is introduced to the desired location, and the needle and related accessories removed leaving the catheter in place. The hole formed in the tissue by the needle usually is larger than the diameter of the catheter allowing fluids to leak from one side of the membrane to the other to cause severe discomfort to the patient. U.S. Pat. No. 4,417,886 issued Nov. 29, 1983 discloses a catheter introduction set for introducing a catheter into a small diameter blood vessel consisting of a catheter mounted on a hollow needle having a spring wire guide therein. In use, the hollow needle is first inserted into the blood vessel, the spring wire guide is advanced into the blood vessel as far as possible and the catheter then advanced on the spring wire guide into the blood vessel. The spring wire guide and needle are removed leaving the catheter in the blood vessel.
U.S. Pat. No. 4,655,750 issued Apr. 7, 1987 discloses another embodiment of catheter system for placement of a flexible catheter into the lumen of an artery or vein which includes a guide wire adapted to be advanced into the lumen and a catheter advanced along the guide wire until placement is achieved.
U.S. Pat. No. 4,529,399 issued Jul. 16, 1985 discloses a method and apparatus for placing a catheter in which a hole is made in a vessel wall by a needle outside a catheter and the catheter advanced on a stylet.
Epidural and spinal anaesthesia require the administration of an anaesthetic agent into the epidural or subarachnoid spaces respectively of the spine. Epidural anaesthesia requires substantially more anaesthetic agent than spinal anaesthesia and, if the anaesthetist inadvertently penetrates the dura-arachnoid membrane while endeavouring to administer an anaesthetic agent to the epidural space, a dangerous quantity of anaesthetic agent can be placed in the subarachnoid space, possibly causing paralysis or even death.
U.S. Pat. No. 4,518,383 issued May 21, 1985 teaches an instrument for epidural and spinal anaesthesia in which an outer hollow Tuchy.TM. needle has a bent pointed tip to locate the epidural space and an inner hollow needle with a pointed tip projecting forwardly of the outer Tuchy.TM. needle in alignment therewith to penetrate the dura with a minimum of cutting of tissue.
U.S. Pat. No. 4,737,146 issued Apr. 12, 1988 discloses another version of epidural catheter in which a rigid epidural needle is inserted into an epidural space and an epidural catheter is introduced through the needle into the epidural space through a lateral opening in the tip of the needle.
It is an object of the present invention to provide a method and system for inserting a spinal catheter to ensure correct placement of the catheter in the subarachnoid space and to obviate leakage of cerebro-spinal fluid from the subarachnoid space into the epidural space of the spine during and after administration of continuous spinal anaesthesia.